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Previous literature has provided contradictory results, so we present the current investigation to provide additional information to assess the suitability of using soak calcination as a pretreatment method to increase the performance of calcined zeolite when used as the supplementary cementitious material. In this study, natural clinoptilolite zeolite was calcined for three hours at 200°C, 400°C, 600°C, 800°C, and 1,000°C, and the effects of calcination on different physical and chemical properties were observed using a range of experimental tests. The impacts of calcined zeolite were investigated in the hydrated system with the replacement of portland cement up to 20 % by mass on hydration kinetics (i.e., heat of hydration, setting time, chemical shrinkage, degree of hydration), drying shrinkage, and compressive strength. Results revealed that calcination minorly decreased the crystallinity, particle size, and peak pore size of the zeolite, leading to a slightly increased external specific surface area, whereas it increased the rate of moisture absorption and pH of zeolite particles. In the hydrated cementitious system, calcined zeolite reduced the workability and heat of hydration and retarded the initial setting time. The calcined zeolite particles absorbed a part of the water from the fresh mixture and expanded volumetrically, which led to a negative volume of chemical shrinkage up to the final setting time and increased the drying shrinkage. As the dosages of calcined zeolite increased, the compressive strength substantially decreased because of the lower degree of hydration. Overall, soak calcination pretreatment decreased the reactivity of clinoptilolite zeolite particles and impacted the performance of calcined zeolite in the blended system.

Previous studies have shown that the partial replacement of portland cement with natural zeolite can improve the strength and durability of cementitious systems. However, the hydration of clinoptilolite zeolite cementitious materials at an early age as well as microstructural development has not been fully understood. In this study, natural clinoptilolite zeolite replaced portland cement at 0, 5, 10, 15, and 20 % by mass as a supplementary cementitious material. Particle size distribution and mineral phase identification of zeolite particles were done by laser diffraction particle size analysis and x-ray diffraction (XRD), respectively. Workability, setting time, chemical shrinkage, heat of hydration via isothermal calorimetry, compressive strength, and degree of hydration were used to assess the effects of zeolite addition on early age properties. Furthermore, pozzolanic activity via thermal gravimetric analysis, chemical and microstructural characterization were accomplished by XRD as well as scanning electron microscopy. Results revealed that the addition of zeolite lowered the heat of hydration and minimized or shifted the tricalcium aluminate (C3A) peak in the heat of hydration curve. Results also indicated that the addition of zeolite likely produced calcium aluminate silicate hydrate (C-A-S-H) at an early age, due to the initial dissolution of aluminate concentration in the alkaline solution. Furthermore, the addition of zeolite can accelerate the early age of hydration by reducing the initial and final setting time of pastes. As zeolite dosage rate increased, compressive strength decreased because of the slow pozzolanic reactivity as well as the lower degree of hydration. Results also showed that zeolite led to the formation of elongated needle-shaped and fibrous hydration products.

The present study explores the potential of producing an alternative ASTM Type IL portland-limestone cement (PLC) using up to 20 % eggshell powder (ESP) by mass as crushed ESP is similar in chemical composition to limestone. To this aim, the hydration, durability, and mechanical properties of the ESP blended cementitious system (using ASTM Type I/II portland cement) are compared to a commercially available ASTM Type IL cement system containing approximately 10 % limestone. ESP was prepared by milling for 3 h upon drying. Characterization of the ESP was done by x-ray diffraction for phase analysis, scanning electron microscopy for microstructural observation, and laser diffraction analysis for particle size distribution. A range of experimental tests were undertaken on both the ASTM Type I/II cement replaced with ESP and the ASTM Type IL systems. Results revealed that the utilization of up to 20 % ESP enhanced the heat of hydration secondary peak (C3A) by increasing the aluminate phase kinetics in the blended system at a favorable pH pore solution. Also, an accelerating effect on the setting time (increased by 20–100 mins) was observed for ESP samples. Chemical shrinkage, compressive strength, and degree of hydration were similar between the ESP and PLC samples. Results also revealed that ESP particles were relatively more effective in minimizing drying shrinkage by 20–35 %, which is attributed to possible internal curing effects. Overall, 10 % ESP blended with ASTM Type I/II cementitious system was similar to the 10 % limestone containing PLC system and could be used as waste material in producing an alternative ASTM Type IL cement.

•Higher temperature heat curing accelerates the onset of delayed ettringite formation (DEF) related expansion but limits the over-magnitude of expansion.•The cement compositions are not responsible alone for the DEF-related expansion, while pore structures can play a significant role in DEF-related expansion.•Expansion may take years to initiate, likely due to a critical pore size threshold necessary to induce stresses. If expansion is delayed, the expansion magnitude is greater than those that expanded immediately.

In order to reduce CO2 emissions, for the automotive industry, the most promising area of research is lightweight construction. Next to weight reduction, lightweight materials like fiber reinforced thermoplastic composites (FRTC) may also improve mechanical properties of vehicle body parts. FRTCs, so-called organic sheets, have the potential for large scale series production and they can be back moulded due to the thermoplastic matrix. On the other hand high production cycle times and a poor surface quality are limiting their potential. Therefore, ITA’s current research approaches these problems in two ways. Nanomodified materials and a new tool concept for heat pressing are going hand in hand and may lead to the technology’s breakthrough.To reduce the cycle times of the production of FRTCs innovative and modified matrix systems are investigated. The goal of the public founded project “VarioOrgano” is to analyze the potential of these modified yarns and the tool system during the FRTC production. Moreover, the capability of these composites in visible parts in automotive applications is investigated. Therefore, the whole process chain from compounding, to melt spinning, commingling and consolidation with a heat press is investigated.This paper shows the production steps along the process chain to produce these FRTCs with focus on hybrid yarn development and production.

•The leachate test results can be used to calculate quasi-crystallization pressures that can give an indication of the expansion potential of mortar samples.•The leaching method may be useful in predicting DEF-related expansion experimentally in 28 days or less.•Sulfate-to-aluminate ratio can also be used as a secondary check for the DEF-related expansion potential.•Higher sulfate-to-aluminate ratio indicates a higher propensity for high DEF-related expansions.

•Milling increased the pozzolanic performance of clinoptilolite zeolite particles in the hydration kinetics of the blended system.•Milling increased the volume of chemical shrinkage due to the increased degree of hydration.•Milling decreased the internal curing capacity of zeolite particles breaking the pore structures, and milled zeolite increased the drying and autogenous shrinkage leading to a higher content of moisture release.•Milling substantially increased the performance of zeolite particles against the alkali-silica reaction due to the adsorption of higher contents of ASR gels by the increased C-S-H networks.

The article presents a research study conducted by the Institut für Textiltechnik (ITA) der RWTH Aachen University to address problems in using fibre reinforced thermoplastic composites (FRTCs) to improve mechanical properties of vehicle body parts.